This invention relates to apparatus for, and methods of, etching a surface of a wafer to provide a fresh and clean surface for providing a deposition on the surface. More particularly, the invention relates to apparatus for, and methods of, etching a surface of an insulating layer in a wafer, and etching walls defining a socket in the wafer, so that the etchings of the surface of the insulating layer, and the etching of the surfaces of the walls in the socket, are smooth and uniform and so that the surfaces do not have any pits.